How to move the master bone of a rig to the actual pose?
You never move the rig in object mode, you want to use the Root/Master bone exactly for this and also you never move the rig away from the Root/Master.

The reason is when you only animate bones, you get only 1 Action. Whereas when you animate also the object you get 2 Actions and it's messy. Can be problem when the rig is linked and you need to apply animations to the proxy. You also can't save such pose to pose library. Etc. this can go on and on why not to do it.

There is no easy way of fixing it. You will have to investigate what bones are parented to the Root/Master, move those bones back and position everything with the Root. And if you have animation do it for every keyframe.

If you have lots of keyframes it might be better to bake the animation. You do this by creating and parenting an empty to each bone that is parented to Root(local axis should correspond). You then bake animation to the empties. Then you move (and animate) the Root where you want it and override the transforms of parented bones with Copy transforms constraints from the empties. Then you bake the animation to the bones and you delete the empties.